Sql query to create relationship between two tables

Creating multiple tables and table relationships

sql query to create relationship between two tables

I need to create a Foreign Key relationship between two SQL Server tables and I would like to know how this is done using the SQL Server. A one-to-one relationship between two entities exists when a particular entity Executing the above SQL statement will create an addresses table, and .. Earlier in this book we looked at how to query data in a database table using SELECT. But we also need to have relationships between these tables. When selecting data from multiple tables with relationships, we will be using the JOIN query. With a database like MySQL, there are two ways to create foreign.

Update Rule - this determines what happens if the row key is updated in the referenced table. The options for the Delete and Update rules are: If not, the change is rolled back. This value would also need to exist in the referenced table. If the value does not exist in the referenced table, the change would be rolled back.

The table designer will open as well as a new window like below. Click on the ellipse Another window will open like below. We can change the Relationship Name Foreign Key name and also need to select the appropriate tables and columns.

On the right, the referencing table Product is already selected, but underneath we need to select the column ProductCategoryID. After making the changes, click OK. At this point we are back to the first Foreign Key screen that we saw. If you scroll down on the right pane, we can see the Delete and Update rules as shown in the image below. In the query design grid, use the Criteria row to enter field criteria. To use a field criterion without displaying the field in the query results, clear the check box in the Show row for that field.

To sort the results based on the values in a field, in the query design grid, click Ascending or Descending depending on which way you want to sort the records in the Sort row for that field.

How to create a SQL Server foreign key

On the Design tab, in the Results group, click Run. Access displays the query output in Datasheet view. An example that uses the Northwind sample database Note: You may want to make a backup copy of the Northwind sample database, and then follow this example by using the backup copy. Suppose you have a new opportunity: They supply every category of food product that you broker. They are a fairly big business, and want your assurances that you can provide them access to enough potential sales to make it worthwhile: Can you provide them with the market they require?

The data you need to answer this question is found in two places: These tables are linked to each other by an Orders table.

sql query to create relationship between two tables

Relationships between the tables have already been defined. In the Orders table, each order can have only one customer, related to the Customers table on the CustomerID field.

Thus, a given customer can have many orders, each of which has many order details. Build the query in Design view Open the Northwind database.

On the Create tab, in the Queries group, click Query Design. All three tables appear in the query design workspace. In the Customers table, double-click the City field to add it to the query design grid.

One-to-One, One-to-Many Table Relationships in SQL Server

This causes only those records where the customer is in one of these two cities to be included in the query. The fields are added to the query design grid. In the ShippedDate column in the query design grid, select the Field row.

sql query to create relationship between two tables

Replace [ShippedDate] with Year: This creates a field alias, Year, that allows you to use just the year portion of the value in the ShippedDate field. In the UnitPrice column in the query design grid, select the Field row. Replace [UnitPrice] with Sales: This creates a field alias, Sales, that calculates the sales for each record. On the Design tab, in the Query Type group, click Crosstab.

sql query to create relationship between two tables

Two new rows, Total and Crosstab, appear in the query design grid. In the City column in the query design grid, click the Crosstab row, and then click Row Heading. This makes city values appear as the row headings that is, the query returns one row for each city. In the Year column, click the Crosstab row, and then click Column Heading. This makes year values appear as the column headings that is, the query returns one column for each year.

In the Sales column, click the Crosstab row, and then click Value.

sql - How to create relationships in MySQL - Stack Overflow

This makes sales values appear at the intersection of rows and column that is, the query returns one sales value for each combination of city and year. In the Sales column, click the Totals row, and then click Sum. This causes the query to sum the values in this column. You can leave the Totals row for the other two columns at the default value of Group By, because you want to see each value for these columns, not aggregate values.

Top of Page View all the records from two similar tables Sometimes, you will want to combine data from two tables that are identical in structure, but one of them is located in another database. Consider the following scenario. Suppose you are an analyst working with student data.

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You are embarking on a data sharing initiative between your school and another school, so that both schools can improve their curricula. For some of the questions you want to explore, it would be better to look at all records from both schools together, rather than each school's records separately. You could import the other school's data into new tables in your database, but then any changes to the other school's data would not be reflected in your database.

A better solution would be to link to the other school's tables, and then create queries that combined the data when you run them. You would be able to analyze the data as a single set, rather than performing two analyses and trying to interpret them as if they were one. To view all the records from two tables with identical structure, you use a union query. Union queries cannot be displayed in Design view.

Creating Primary and Foreign Keys in SQL Server 2012

Create a union query by using two tables On the Create tab, in the Queries group, click Query Design. A new query design grid opens, and the Show Table dialog box appears. In the Show Table dialog box, click Close. On the Design tab, in the Query Type group, click Union. The query switches from Design view to SQL view.

At this point, the SQL view object tab is empty.

sql query to create relationship between two tables

Field names should be enclosed in square brackets, and separated by commas. The cursor moves down one line in SQL view.